Fantastic work on the models!
Have you got some games in yet? EpicA is an excellent game

I've moved to Bristol relatively recently and I'm looking to in a while (I'm still gradually unpacking my collection). There's an Epic-UK tournament in Bristol this month, though its sold out already, but there's another couple of close ones in Bath and Cardiff Feb and Mar and the tournaments see very welcoming of newer players.
Dave Fraser wrote:
They're currently on 40mm rounds for painting which feels about right but I could go up to 50s and not feel lost. Before I base them I I thought I'd best check what size people use for this size of titan?
I realise this is now a rather old question, but you're free to go for whatever you want that seems / looks reasonable. There are no fixed rules for vehicle / WE basing and official models have varied e.g. GW sold Warhounds on 40mm bases but the FW ones were sold on 60mm bases. Anywhere in the region of 30-60mm would seem fine for Revenants I would think.
Personally I use and recommend
Fenris Games laser cut ply bases as they come in a tonne of different shapes and sizes - 20, 25, 30, 40, 50, 60, 70, 80 100mm rounds just to pick one example. They're also 1.5mm high, similar to the stands the epic models come on. Some people model titans on higher bases, like 40k height bases, but it's always looked a off to me aesthetically having the different height ones mixed together.